New "marshmallow test" suggests trust matters

Evelyn Rose, 4 of Brighton, N.Y., participates in a reenactment of the marshmallow experiment used in a University of Rochester study published in the journal Cognition. The study was conducted at the University of Rochester Baby Lab.

The legendary marshmallow test psychological experiment has gotten an update in a new study. While the test still shows that some kids are willing to wait longer for an extra marshmallow, the new study suggests the trustworthiness of the person promising the added reward may also play a role.

In the original 1972 Stanford marshmallow experiment, scientists looked at more than 600 children between the ages of four to six to study the effects of "delayed gratification." Children were put in an otherwise empty room with a snack of their choosing -- either an Oreo cookie, marshmallow or pretzel stick -- and were told they could eat the snack now or wait 15 minutes and get a second snack. Many of them engaged in distracting behavior, such as kicking the table, covering their eyes or pulling on their hair, to get through the task. One-third of the children were able to hold off for the full duration to get the reward.

In the updated version, scientists tested not only the child's ability to wait, but also wanted to see if the reliability of the person who was supposed to provide the incentive played any part.

Lead author Celeste Kidd, a doctoral candidate in brain and cognitive sciences at the University of Rochester in Rochester, N.Y., told USA Today that she was inspired to attempt the experiment when she was volunteering at a homeless shelter and saw a little girl eating a lollypop. When the child was about to eat the treat, an older boy stole it from her. Instead of crying, she didn't seem that upset, which perplexed Kidd. She then realized that these children likely weren't upset because they had adapted to the unreliability of their environment.

To test reliability's role in delayed gratification, researchers divided a group of 28 children, ranging in ages from 3 to 5, into two groups.

For the first group -- the unreliable group - the children were given bad art supplies and told that if they waited, they could get better materials. The researcher however would return 2.5 minutes later without anything, saying it was a mistake and there weren't extra art supplies.

Then these children were given a sticker and told that if they waited to use the sticker, they would get better stickers. The researcher would leave again and return 2.5 minutes later empty-handed. The same scenario was repeated for the reliable group -- except this time the researcher returned with what they promised.

Then, the experimenters gave all the children a marshmallow in a plain room and told them they could have one marshmallow now or wait for the researcher to come back and have two marshmallows instead. The parents and scientists watched the children and recorded how long it took them to have the first taste or if 15 minutes had elapsed. At the end of the experiment, everyone was rewarded with three additional marshmallows.

What astonished researchers was that kids who were in the unreliable group waited three minutes and two seconds before eating the marshmallow, while children in the reliable group who trusted the researcher held out for 12 minutes and two seconds. Only one child in the unreliable group waited the entire 15 minutes, whereas nine kids in the reliable group didn't snack the entire time.

"I was astounded that the effect was so large," co-author Richard Aslin, the William R. Kenan Professor of brain and cognitive sciences at the University of Rochester in Rochester, N.Y., said in a press release. "I thought that we might get a difference of maybe a minute or so... You don't see effects like this very often."

In both groups, the kids tried different ways to hide or ignore the marshmallow including dancing, singing or taking pretend naps. Some nibbled at the bottom of the marshmallows in order to hide their bites.

"Watching their strategies for waiting was quite entertaining," says Holly Palmeri, coauthor and coordinator of the Rochester Baby Lab, said in a press release. "We had one little boy who grabbed the marshmallow immediately and we thought he was going to eat it," recalled Kidd. "Instead of covering his eyes, he covered the marshmallow (by sitting on it)."

Aslin said the study shows that kids are more reliant on their parent's overall reliability or unreliability, but one single situation won't completely change their mind about how the world works.

"Don't do the marshmallow test on your kitchen table and conclude something about your child," Kidd added. "It especially would not work with a parent, because your child has all sorts of strong expectations about what a person who loves them very much is likely to do."